Problem: Rewrite ${\dfrac{7^{-10}}{7^{8}}}$ in the form ${7^n}$.
Explanation: ${ \dfrac{7^{-10}}{7^{8}} = 7^{-10-8}} $ ${ \hphantom{\dfrac{7^{-10}}{7^{8}}} = 7^{-18}} $